1. Field of the Invention
The present invention relates to a semiconductor integrated circuit, and in particular, relates to a data matching circuit (a signal agreement/non-agreement detection circuit) which determines whether the difference between values expressed by two signals is smaller than a predetermined value or not.
2. Related Art
In the fields of data processing and automated control, the comparison of data expressed as numerical values, and a determination of agreement or non-agreement (whether the difference between the values is within a pre-specified range or not) plays an extremely important role. For example, in the field of image processing, when the checking of image data is conducted, the image is divided into a number of picture elements, and a determination is made as to whether the various picture element data are in agreement with (match) a value serving as a standard which is recorded in advance, and if the number of picture elements among all the picture elements which are in agreement is above a predetermined number, the image is determined to be identical to a recorded image. Accordingly, it is necessary to rapidly execute a determination of agreement/non-agreement for an extremely large number of picture element data. In consideration of a broad range of applications, it is necessary that the recorded value which serves as the standard of comparison be variable. Conventionally, with respect to such uses, functions were realized by means of software using a computer. However, the data matching function realized using software was slow in operation, and it was impossible to employ such a function in the field of image processing and the like, which requires high-speed operation.
In order to execute data matching at high speed, realization in terms of hardware (electrical circuits) is necessary. By means of installing a plurality of data-matching circuits, realized in terms of hardware (electrical circuits), and operating these in parallel, it is possible to execute an extremely large number of data matchings at high speed. When constructing matching circuits using hardware employing conventional technology, the circuitry is complex, and a large number of elements is required, so that the surface occupied by the circuits becomes undesirably large. Accordingly, there is a limit to the number of matching circuits which could be installed on a single semiconductor chip, and when conducting the matching of image data such as that described above, it was essentially impossible to produce an integrated circuit chip on which matching circuits corresponding to a number of picture elements were installed and parallel processing was conducted so as to conduct matching at high speed.
The present invention has as an object thereof to provide a semiconductor integrated circuit which is capable of conducting high-speed data matching employing simple circuitry.